I am taking a road trip with my wife in April around Easter to Florida. Either on way down or way back up, which will be weekend after Easter, I want to spend a night in Atlanta. I was wondering about driving through the mountains to get there... do I need to drive a rental car in Low Gear at all on route 75 or 24? I drove down to Florida about 7 years ago and I drove through the mountains the wrong way....I used breaks. Since then I have learned you want to break with engine and drive in Low Gear in the mountains. I though don't recall on 75 or 24 any really steep slopes though.....If I remember it was pretty smooth and easy driving. I remember 24 had a lot of winding curves, but that really wasn't bad.. I was going take either 75 all the way through Kentucky and Tenn or I was going to take 65 ->24-> 75.

Do I even need to worry about driving in Low Gear in a car on either 75 or 24?

I have driven the mountains on 75 more times than I can count. I don't recall ANY that required the type of driving you are describing. In Colorado, yes, I have. The answer is no.

It's not a problem or a worry, just the way you need to drive sometimes. I still use brakes in some mountains in WV and VA around where I live when I go skiing or hiking or something. You should be able to tell by the feel of the car's engine and conditions, but I'd say to consider it if you are on a grade maybe more than 6 pct. I don't usually do that on a 7% or lower grade, unless it's a smaller narrow road that is winding or it goes on for miles, then it's different. Today I drove on I68 that had a 7 pct grade and I didn't downshift, but it's a wide road and no sharp turns and it didn't last miles. If there are signs warning you of the steep grade and warning trucks, maybe think about it. Not just going down, either.

There is a 5-6 pct grade on I75 around the TN/KY border, I think that's the steepest. But if you take 65 to 24, you won't be on that section. There are steep grades on I24 between Murfreesboro and Chattanooga, like Monteagle Mtn area can be dangerous for trucks because it's so long, but it's still only about 6 pct grade. But for four miles, that's the issue, so be careful of other cars and trucks for sure. Johnny Cash wrote a song about how dangerous that section is.

When I started down Monteagle,
the brakes just wouldn’t hold.
I knew I was in trouble
and ’bout to lose control.
The runaway ramp was waitin’,
I saw the warning sign.
I said, ‘Lord help me make it –
have mercy on this soul of mine.’

credit to
https://www.overdriveonline.com/busi...-knuckle-roads

ON these hightways it was always interesting to see if the truck ramps had been used recently--and it IS a nightmare for a trucker I am sure.